I don't like the idea. First off, it is unreasonable to expect a 3rd party (Pekka) to be in any way involved in your personal transactions just because he provides the medium for communication. Is the phone company responsible for telephone fraud?
The second thing that bothers me is the arbitrary $2500 point. Is it OK to steal lesser amounts from people? I don't want to be ripped off for $2499 and have no assurance or recourse, while you get ripped off for $2500 and have some/any protections.
The whole idea puts more personal information out where YOU/I have no control over what happens to it. That hardly seems like an increase in your personal financial security.
While holding the thief in question wholly responsible for his actions, the victim in the referenced crime had indications that this transaction may not be legitimate. On the internet, a thief can only steal from a willing victim. No gun in your face or knife in your back here. Bottom line: you are on your own in this jungle - act accordingly. Jungle = online transactions. Not singling out POTN. This is true everywhere. The same applies to Craigslist and other such organizations. Its your money. Be particular about who you give it to. Don't expect anyone to care more about your money than you do.
Forty years ago, I made fake IDs to get into bars and nightclubs. Modern technology makes that a lot easier than it was in the '70s. How exhaustive will the 'background' check be? Who is paying for it?
Who is responsible when someone circumvents the system. If I lose $5000 buying a phantom 1DXII, is Pekka going to send me a check?
How is the system policed? You sell me item X, legitimately describing it and I have a bad day and claim you ripped me off. Now what? Who is spending time and/or money to sort that out?
I like the current system. It appears to work well, for me anyway. But I am a suspicious old curmudgeon. Then again, I honestly describe the items I sell. I actually own the items I sell. I actually ship the items I sell. If I am buying, I check reputation. If POTN reputation is thin, I ask for more. When more is provided, I contact the seller through the alternative method (E-bay, web-site, photography business, FM, Camel), just to make sure they are one and the same person. I strive to maintain an excellent online reputation. I think the idea posited in the original post will diminish the reputations of those of us who choose not to participate. I know I won't. That does not make me dishonest. It makes me cautious.